The project is a study of mucociliary transport in patients with cystic fibrosis. Tracheal mucociliary transport rates are measured by visual tracing (through a flexible bronchoscope) of the movement of Teflon discs across the tracheal mucosa. The effects of various drugs (such as beta-adrenergic agonists) or therapeutic manipulations (such as inhalation of aerosols) are studied in an attempt to develop therapeutically useful techniques for improving pulmonary clearance of secretions. In selected patients, biopsies of tracheal epithelium will be studied by electron microscopy to correlate measured rates of mucociliary transport with surface ultrastructure.